1. Field of the Invention
The present invention relates to check valves and, more particularly, to what is called a poppet type check valve in which a valve element (check valve element) displaceably provided in a housing and urged to seat on a valve seat is unseated from the valve seat by an upstream-side fluid pressure to permit flow of fluid in one direction from the upstream side toward the downstream side.
2. Description of the Related Art
At a hydrogen supply station for supplying hydrogen to hydrogen automobiles, for example, a female coupling member (socket) at the distal end of a supply hose extending from a station tank storing gaseous or liquid hydrogen under high pressure and low temperature is coupled to a male coupling member (plug) at an outer end of a hydrogen inlet pipe extending from a hydrogen storage tank of a hydrogen automobile to supply hydrogen. The male coupling member is provided therein with a check valve that permits flow only from the supply hose to the hydrogen storage tank of the hydrogen automobile and that blocks the reverse flow.
When a poppet type valve is employed as the above-described check valve, the following problem may arise: As filling of hydrogen into the hydrogen storage tank of the hydrogen automobile progresses, the pressure in the hydrogen storage tank approaches the pressure in the supply hose of the hydrogen supply station, and the pressure difference between the upstream and downstream sides of the check valve decreases. Consequently, urging force that urges the valve element to seat on the valve seat and the pressure difference become equal to each other, so that seating and unseating of the valve element on and from the valve seat are repeated frequently, causing what is called chattering. Such chattering hinders the supply of hydrogen in stable condition and leads to problems such as the occurrence of noise and degradation in durability of the valve element and the valve seat.
To solve the above-described problem, there has been developed a check valve in which a flow path is formed in the valve element to allow fluid flowing in through the valve seat to pass through the flow path, and in which the flow path is configured to have a high flow resistance, thereby preventing the occurrence of a rapid pressure change across the valve element, and thus attempting to solve the above-described problem (Patent Literature 1).